On Thu, Dec 13 2007, Mark Lord wrote: > Mark Lord wrote: > >Jens Axboe wrote: > >>On Thu, Dec 13 2007, Mark Lord wrote: > >>>Matthew Wilcox wrote: > >>>>On Thu, Dec 13, 2007 at 01:48:18PM -0500, Mark Lord wrote: > >>>>>Problem confirmed. 2.6.23.8 regularly generates segments up to > >>>>>64KB for libata, > >>>>>but 2.6.24 uses only 4KB segments and a *few* 8KB segments. > >>>>Just a suspicion ... could this be slab vs slub? ie check your configs > >>>>are the same / similar between the two kernels. > >>>.. > >>> > >>>Mmmm.. a good thought, that one. > >>>But I just rechecked, and both have CONFIG_SLAB=y > >>> > >>>My guess is that something got changed around when Jens > >>>reworked the block layer for 2.6.24. > >>>I'm going to dig around in there now. > >> > >>I didn't rework the block layer for 2.6.24 :-). The core block layer > >>changes since 2.6.23 are: > >> > >>- Support for empty barriers. Not a likely candidate. > >>- Shared tag queue fixes. Totally unlikely. > >>- sg chaining support. Not likely. > >>- The bio changes from Neil. Of the bunch, the most likely suspects in > >> this area, since it changes some of the code involved with merges and > >> blk_rq_map_sg(). > >>- Lots of simple stuff, again very unlikely. > >> > >>Anyway, it sounds odd for this to be a block layer problem if you do see > >>occasional segments being merged. So it sounds more like the input data > >>having changed. > >> > >>Why not just bisect it? > >.. > > > >Because the early 2.6.24 series failed to boot on this machine > >due to bugs in the block layer -- so the code that caused this regression > >is probably in the stuff from before the kernels became usable here. > .. > > That sounds more harsh than intended --> the earlier 2.6.24 kernels (up to > the first couple of -rc* ones failed here because of incompatibilities > between the block/bio changes and libata. > > That's better, I think! No worries, I didn't pick it up as harsh just as an odd conclusion :-) If I were you, I'd just start from the first -rc that booted for you. If THAT has the bug, then we'll think of something else. If you don't get anywhere, I can run some tests tomorrow and see if I can reproduce it here. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
